Cleavage surfaces, dislocations

Clean single-crystal surface, 15 31 Clean surfaces, alcohol reactions, 29 37-38 Clear Air Act of 1970, 24 59, 62 Cleavage surfaces, dislocations on, 19 331-333 ClOj, ESR of, 22 309... 

Figure 5-54. Extensions of the Rice-Thompson model suggest a) how modes II and HI components can translate the mixed mode line down the dislocation emission surface until it intersects with the cleavage surface giving fracture, and b) how hydrogen might translate the cleavage surface until it intersects the load line, producing embrittlement after substantial emission (Gerberich et al., 1992).

To certify that dislocations are truly responsible for the etch pits two criteria are generally employed (i) surfaces that have been separated by cleavage must yield 65a) matched etch patterns, as in Fig. 30 and (ii) continued etching must not, in general, alter the number of etch pits on a given surface, as in Fig. 31. Dislocation loops are often conveniently revealed (63) by dislocation etchants because, upon successive etching. 

The work of fracture may be characterized by a critical energy-release rate for cleavage G . A crack propagates in the absence of a plastic strain if the equality ( deav 2y holds, where ys is the surface energy. If a nucleation and motion of dislocations occur at the tip of the crack the stress concentration relives. A critical... 

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